Any idea why this shift shaft seal would be leaking?

Trans work sucks. No matter how long you drain the trans fluid, there will be 1 cup left under the valve body and no amount of pans will catch all the drips. At least that is what Ive found. The drips seem to travel to all points of the compass and drop right outside the catch pans footprint. Whomever created the trans pan with the drain plug deserves a beer. I would have tapped that seal in flush before changing it out. May have been a 5 minutes job with a deep socket on top and a crowbar forcing it down or C-clamp if you got one that ballsey.